Facebook: your IP address is public
See that header in your Facebook notification email that looks like this?
X-Facebook: from zuckmail ([NzYuMTY5LjIzLjU2])
That's your friend's IP address:
% perl -MMIME::Base64 -le 'print decode_base64("NzYuMTY5LjIzLjU2")'
as of I wrote this entry, it still there.